1991-2020 Degrees Fahrenheit 1 39.9 38.2 1.7 56 21 1978 1976 1961 1957 top-third 1986 2 36.4 36.6 -0.2 44 33 1978 2017 1961 1957 normal 3 36.5 37.4 -0.9 40 37 1977 2017 1961 1960 normal 2007 4 38.9 39.6 -0.7 37 39 1977 2017 1961 1957 normal 1975 5 42.3 43.1 -0.8 36 40 1977 2017 1961 1960 normal 6 47.1 47.3 -0.2 45 30 1977 2017 1961 1960 normal 1960,2021 7 51.0 51.2 -0.2 47 28 1977 2017 1961 1960 normal 1989,1997 8 53.8 54.3 -0.5 41 34 1977 2017 1961 1960 normal 1988,1998 9 55.4 56.3 -0.9 26 49 1977 2017 1961 1960 normal 1955,1956,1965,1993 10 55.8 57.1 -1.3 24 51 1977 2017 1961 1960 bottom-third 11 55.3 57.1 -1.8 11 64 1977 2017 1962 1961 bottom-third 12 54.6 56.2 -1.6 18 57 1977 2017 1961 1960 bottom-third 1985,1996 18 51.5 53.2 -1.7 14 60 1978 2017 1959 1961 bottom-third 1966,1980 24 54.2 56.1 -1.9 7 67 1978 2017 1962 1961 bottom-tenth 2015 36 54.9 56.1 -1.2 19 54 1979 2018 1961 1960 bottom-third 1959 48 54.7 56.1 -1.4 14 58 1964,1980 2020 1962 1961 bottom-third 1983,1984 60 54.7 56.1 -1.4 13 58 1981 2020 1962 1961 bottom-third 1969,1983,1984,1985